1. Field of the Invention
The present invention relates to a jack and in particular to a keystone jack with a double-cross isolation structure to avoid the crosstalk phenomenon.
2. Description of Prior Art
When the electronic signals are transmitted along the layouts of the printed circuit board, the electromagnetic waves of the electronic signals are transmitted from one side of the integrated circuit to another side of the integrated circuit along the layouts of the printed circuit board as well, so the crosstalk happens. Due to the electromagnetic induction, the voltages and the currents are varied transiently by the electromagnetic waves in the transmission process.
The electromagnetic waves are induced by the electric fields and the magnetic fields with time variation. In fact, the electric fields and the magnetic fields exist not only in each kind of layouts in the printed circuit board. The energy of a plenty of electromagnetic waves exists outside the layouts. So when the electronic signals are transmitted along the lead wire and there are other wiring lines nearby, other wiring lines will be impacted by the electric fields and the magnetic fields of the electronic signals.
According to the Maxwell equation, the electric fields and the magnetic fields will induce the voltages and the currents in the lead wire nearby, so the electric fields and the magnetic fields induced from the transmission process of the electronic signals will cause the electronic signal interferences. This phenomenon is called the crosstalk phenomenon.
Beside the crosstalk phenomenon in the printed circuit board mentioned above, the crosstalk phenomenon exists in the conventional keystone jacks or other connectors as well. The distance of the pins of the puncturing terminals is short because the volume of the keystone jack is small. The core wires are closed because the distance of the pins of the puncturing terminals is short, so that the electricity is not stable when the electronic signals are transmitted. The electromagnetic waves induced by the puncturing terminals will impact the puncturing terminals nearby, so that the impedance characteristics are not stable and the transmission signals are decayed.